Method for chemically polishing lead



I W W Sept. 21, 1954 c, SIMON 2,689,785

METHOD FOR CHEMICALLY POLISHING LEAD Filed March 18, 1953 |OO% HYDROGENPEROXI DE wi /OWNER w t HYDROGEN so /\A/\/\/\/\/\/\/\/\/\/\ 40 PEROX 1DE ALALLLLA 7o AYAYAYAYAYAYAYAYAYAYAYAVAYA 3OAYAVAVMYAYAYAYAYAYAYAVAYAYA AVAVAYAVAAAVMVAYAYAYAYAYAYA '00 IO 4O 5O 6O7O O0 WATER wto/Q ACETIC ACID ACETIC ACID INVENTOR ALBERT C. SIMON i BYfi m ATTORNEYJ Patented Sept. 21, 1954 UNITED STATES PATENT OFFICEMETHOD FOR CHIIJBIIQQISALLY POLISHING Albert C. Simon, Arlington, Va.

United States of America as r Secretary of the Navy Application March18, 1953, Serial No. 343,267

2 Claims. (Cl. 41-42) (Granted under Title 35, U. S. Code (1952), sec.266) solutes are presen hard metals such as steel can be polished to aof the polishing high degree of smoothness approaching a high lustrecondition by mechanical polishing, that is by buffing the surface withthe aid of fine abradent' pastes. Lead, on the other hand, being arelatively soft metal cannot be worked up by buffing with the aid offine abradent pastes to a smoothness of surface which approaches that ofa high luster polish. The soft metal tends to tear under the action ofthe abradent and particles of the abradent become 2 embedded in thesurface of the lead.

Lead as a metal for ornamentation purposes finds little acceptance byreason of the fact that mechanical polishing of the metal even bybuflfing, with aid of fine abradent pastes, does not produce a highfim'sh of pleasing appearance to the eye, but one which although brightlacks tone and in color partakes stronglyof the nature of the metal,being of a lead-like gray cast.

It is a principal object of the invention to pro-- acetic acid and wi h1 vide a method for chemically polishing lead which is productive ofpolished lead surfaces of high luster. It is a further object to providea method for improving the surface of lead for the plating of metalsthereon. It is a still further object to K Peroxide 0f ample, Superoxal(h the proper proportions o of water and stirring the provide a methodfor rendering lead more attractive as a metal for ornamental purposes.

These and other objects are accomplished in accordance with the presentinvention in a method which comprises subjecting lead having a smoothsurface in clean condition to vigorous agitation for a very short timein a polishing solution of hydrogen peroxide in aqueous acetic acid, thecomposition of which is hereinafter more fully set forth, until a highluster is attained on a ur of the lead s the lead surface and thenquickly removing the polishing solution from the treated lead.

I have found that a polish of high luster approaching in brilliance andtone that of nickel and chrome finishes can be imparted to clear, clothbuffing wheel smooth lead surfaces by polishing them in accordance withthe method of the invention with a solution in water of between about 10and,25 EY/"wight'hydrogen peroxide and between about 15and 7oz, byweight acetica i d in which these assignor to the epresented by the 2 tin inverse tions may -be made up,

tion of the ingredients.

The smooth condition of the lead surface to be chemically polished bythe method of the invenate ydrogen peroxide 3 r. These preferred soluforexample, with 13% wn concentration, for exe calcu' lated amount mixtureto effect solu- 3 from the polished lead surface by washing with water.4

In the practice of the method of the invention,

- the lead surface to be polished, which may be of any geometricalpattern, is separately introduced into and agitated in the aqueouspolishing solution of hydrogen peroxide and acetic acid. If more thanone lead article is to be treated in the polishing bath at the same timecare must be taken to avoid contact of the articles with each othersince atomic welding of the articles to one another will take place inthe presence of the polishing solution. Suitably, the lead articles tobe polished are separately suspended in the polishing bath by means of awire, hook or clamp attached to a disposable extension or tab on thearticle as is practiced in the metal plating art, or the articles areindividually containedin a wire basket. The suspending or supportingmeans for the lead articles should be made of an acid resistant materialsuch as aluminum or stainless steel. The time required for producing apolish of high luster on the smooth lead surface is very small, beingbut a matter of seconds. The lead article is vigorously agitated in thepolishing bath for only such time as is required to observe thedevelopment of the high luster on the lead surface. It is then removedand promptly washed with aqueous acetic acid of a concentration notappreciably lower than that of the acetic acid in-the polishingsolution. Wash acid of a concentration in acetic acid which is up toabout 5% less than that of the polishing solution can be used. Byobserving this practice in respect to the washing of the polished leadsurface, not only is the polishing solution removed therefrom but,importantly, the introduction of any substantial amount of water intothe polishing solution on the treated leadarticle is thereby avoided andby consequence, roughening of the polished surface. For a given contentof hydrogen peroxide in the polishing solution, an increase in the watercontent and a decrease in the acetic acid content thereof causesroughening of the lead surface'due to the fact that such dilutedsolutions attack the lead more vigorously.

The smooth lead surface should be clean before being subjected to thechemical polishing. In some instances this may require only the thoroughwashing of the lead surface with water. In others the use of organicsolvents such as benzene may be required for the removal of greasymaterials from the lead surface.

The invention is further illustrated by the following specific exampleof the application of the method to the polishing of a lead surface.-Percentages of reagents are by weight.

Example A lead article in the shape of a pedestal having integrallymounted thereon a one-half inch diameter sphere was buffed to produce afairly smooth surface on the sphere. The bufling was done with a clothbufiing wheel using a buffing paste composed of powdered magnesiumcarbonate and water. The buffed lead surface was thoroughly washed withwater to remove the 4 bufiing paste, rinsed with dilute (540%) aceticacid and quickly, while wet, immersed in a solution in water of 15%hydrogen peroxide and 50% acetic acid. The article was held by thepedestal portion while the sphere portion was vigorously agitated in thepolishing solution. A polish of high luster was obtained on the surfaceof the sphere in a matter of a few seconds, almost instantly. Thepolished sphere was quickly washed with acetic acid of 50% concentrationto remove the polishing solution and then with warm water to remove theacetic acid. The polished lead article is dried by an air blast or inany other way found suitable.

In the event that the polished lead article is to be plated with metal,such as copper, silver and the like, it is not dried but entered intothe plating bath directly after the water wash in order to retain themaximum benefit of the clear, highly polished surface.

The high luster polish obtainable on lead surfaces by the method of thepresent invention is quite resistant to tarnishing in the atmosphere andmay be conserved by coating the polished surface with a clear lacquer.

While I have described a specific embodiment of my invention by way ofillustration, it is to be understood that the invention is not to belimited thereto but only as is required by the prior art and theappended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of American for governmentalpurposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A method of producing a polish of high luster on a lead surface whichcomprises immersing the lead surface in clean smooth condition into anaqueous polishing solution of hydrogen peroxide and acetic acid andvigorously agitating it therein for a time sufiicient to develop apolish of high luster thereon, quickly washing the polishing solutionfrom the lead surface with aqueous acetic acid of a concentration notanpreciably less than that of the polishing solution and then washingthe lead surface with water to remove the acetic acid, said polishingsolution containing between about 10 and 25% by weight hydrogen peroxideand between about 15 and by weight acetic acid in inverse proportion andV in a weight ratio of acetic acid to hydrogen peroxide which for eachunit of 5 weight percent .of acetic acid decreases with increase in thehydrogen peroxide content by a factor which is about 3.3% for each 1%increase in weight of the hydrogen peroxide.

2. A method as defined in claim 1, wherein the aqueous polishingsolution contains between about 13 and 17% by weight hydrogen peroxideand between about 60 and 42% by weight acetic acid.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,446,060 Pray et a1. July 27, 1948

1. A METHOD OF PRODUCING A POLISH OF HIGH LUSTER ON A LEAD SURFACE WHICHCOMPRISES IMMERSING THE LEAD SURFACE IN CLEAN SMOOTH CONDITION INTO ANAQUEOUS POLISHING SOLUTION OF HYDROGEN PEROXIDE AND ACETIC ACID ANDVIGOROUSLY AGITATING IT THEREIN FOR A TIME SUFFICIENT TO DEVELOP APOLISH OF HIGH LUSTER THEREON, QUICKLY WASHING THE POLISHING SOLUTIONFROM THE LEAD SURFACE WITH AQUEOUS ACETIC ACID OF A CONCENTRATION NOTAPPRECIABLY LESS THAN THAT OF THE POLISHING SOLUTION AND THEN WASHINGTHE LEAD SURFACE WITH WATER TO REMOVE THE ACETIC ACID, SAID POLISHINGSOLUTION CONTAINING BETWEEN ABOUT 10 AND 25% BY WEIGHT HYDROGEN PEROXIDEAND BETWEEN ABOUT 15 AND 70% BY WEIGHT ACETIC ACID IN INVERSE PROPORTIONAND IN A WEIGHT RATIO OF ACETIC ACID TO HYDROGEN PEROXIDE WHICH FOR EACHUNIT OF 5 WEIGHT PERCENT OF ACETIC ACID DECREASES WITH INCREASE IN THEHYDROGEN PEROXIDE CONTENT BY A FACTOR WHICH IS ABOUT 3.3% FOR EACH 1%INCREASE IN WEIGHT OF THE HYDROGEN PEROXIDE.